In a microdisplay-based projection display system, light from a light source may be modulated by the microdisplay as the light reflects off the surface of the microdisplay or passes through the microdisplay. Examples of commonly used microdisplays may include digital micromirror devices (DMD), deformable micromirror devices, transmissive, reflective, or transflective liquid crystal, liquid crystal on silicon, ferroelectric liquid crystal on silicon, and so forth. In a digital micromirror device (DMD)-based projection system, where large numbers of positional micromirrors may change state (position) depending on an image being displayed, light from the light source may be reflected onto or away from a display plane.
For image quality reasons, it may be desirous to maximize the brightness of the images being displayed. In general, the brighter the images, the better the perceived image quality. Therefore, there have been many techniques utilized to help improve image brightness. Some of the techniques may include increasing the brightness of the light source, using multiple light sources, and so forth.
In a laser illuminated, microdisplay-based projection display system, it may be possible to maximize image brightness by increasing the duty cycle of the laser(s) used to illuminate the microdisplay. Scanning the light produced by the laser(s) so that more than one color of light may simultaneously illuminate the microdisplay may be performed to increase the duty cycle of the laser(s). That is, if only one color of light may illuminate the entire microdisplay at a time, then all of the other lasers must be turned off. However, if scanning permits the light from a first laser and the light from a second laser to illuminate different portions of the microdisplay, then the on-time of the first and the second lasers may be increased, thereby increasing the duty cycle of the lasers.
However, the light, produced by the laser(s), should be uniform or relatively uniform to produce a uniformly illuminated image on the display plane when scanned. If the light is not sufficiently uniform, variations in illumination may be seen in the image. Furthermore, if multiple colored lights are used, then the multiple colors of lights should have substantially identical intensity profiles to prevent the appearance of color bands in the image on the display plane.